Simplified Message Desk Interface
（重定向自SMDI）
Simplified Message Desk Interface (SMDI) is a protocol that defines the interface between a voice mail system and a phone system such as a PBX or public telephone switch. It was developed by Bell Labs. It is used to provide the voice mail system the information it needs to process the call. Each time a call is sent to the voice mail system, a message is sent using SMDI over a serial interface that identifies the line, the type of call, and the calling/called party numbers. The SMDI protocol also specifies a method for turning the message-waiting indicator (MWI) on and off on individual telephones.